Getting the overload set of a template

[Alex]

On Saturday, 21 April 2018 at 19:51:05 UTC, Simen Kjærås wrote:
> On Saturday, 21 April 2018 at 11:23:33 UTC, Alex wrote:
>> So, do you mean, that the constraint belongs to the interface 
>> of a template?
>
> Not necessarily - it depends on what you want to achieve. The 
> only thing I mean is that the code clearly defines two 
> templates in one case (and chooses which template to 
> instantiate based on the arguments), and one template in the 
> other (and chooses the contents of that template based on the 
> arguments).

This is wrong, at least as I understand this:
Lowering rules apply. These rules define a set of semantic 
equivalent constructs. I expect all semantic equivalent 
constructs to be handled equivalent.**


> Sure, the end result may be similar*, but how it works in the 
> language is clearly defined, and different between the two 
> cases.
>
> *In this case, there are important differences - in the first 
> case the template itself is marked with a UDA, in the second 
> the enum member is.
This is a good point. But you won't be able to get the UDA from 
an uninstantiated template will you? If you will, then, I'm 
wrong, I think...

** So my point is: If you can transform some construct into 
another one by lowering rules, than
- either: you can't define an overload
- or: you can define same overloads on both forms.
[1]

> In the first case foo!"c" will fail to instantiate, in the 
> second it won't.

This is due, I didn't add
´´´
else
{
     assert(0);
}
´´´
sorry for this.

[1] 
http://www.drdobbs.com/architecture-and-design/so-you-want-to-write-your-own-language/240165488?pgno=2